Dependence on Cardiac Contractility Modulation Therapy: Loss of Continuous and Effective Modulation as a Cause of Heart Failure Exacerbation.

Cardiac contractility modulation (CCM) is a device-based therapy for patients with heart failure, reduced left ventricular ejection fraction (LVEF), and narrow QRS who are not candidates for cardiac resynchronization therapy. CCM delivers non-excitatory impulses during the absolute refractory period, improving myocardial contractility without increasing oxygen consumption. We report a 58-year-old man with dilated cardiomyopathy and persistent New York Heart Association (NYHA) class III symptoms despite optimal therapy who underwent CCM implantation. The patient initially showed significant clinical improvement, with increased LVEF and functional status. However, several years later, he developed clinical deterioration associated with intermittent loss of effective CCM delivery. Surgical revision revealed insulation defects in all three leads, likely due to mechanical interactions. Lead replacement restored CCM function, resulting in marked and sustained improvement in exercise capacity, LVEF, and N-terminal pro B-type natriuretic peptide over long-term follow-up. This case highlights the importance of continuous and effective CCM delivery, as well as the need for careful long-term monitoring of device integrity, particularly in patients with multiple intracardiac leads.